The present invention relates to a silicone windshield wiper blade. More particularly, the present invention relates to a tintable, moldable, platinum group metal catalyzed silicone composition, and a method of converting it to a silicone windshield wiper blade exhibiting superior service life.
As discussed by Gibbons et al., U.S. Pat. No. 5,283,927, although silicone rubber is superior to natural or synthetic organic rubbers in many respects, when used for windshield wiper blades, silicone rubber has been found to have an unacceptably high coefficient of friction with respect to glass. For example, a silicone rubber wiper blade can either tear loose from the wiper arm, or it can produce an annoying loud squeak. Gibbons et al. further teach that if the specific gravity of the silicone rubber wiper blade is below a prescribed minium, such as 1.3, frictional force problems can occur with respect to contact between the wiper blade and glass.
It has been found that although cureable silicone compositions can be fabricated with excess filler to produce silicone rubber products, such as a wiper blade having a specific gravity above 1.3, such excess filler loading can have an adverse effect on the performance or service life of the fabricated product as a result of a reduction in physical properties, such as tensile strength. In addition, although pigments are sometimes used in the manufacture of rubber products, the presence of excess filler in fabricated silicone rubber often interferes with the brightness of such pigments. Experience has shown that pigments capable of reflecting incident light within a wave length range of 390 nm to 770 nm can be substantially masked in the presence of excess filler. In addition, the presence of up to 20 parts of a lubricity additive, for example polytetrafluoroethylene, or molybdenum disulfide, in a silicone windshield wiper, such as shown for example by Hamilton et al., U.S. Pat. No. 3,972,850, may also adversely effect the service life of a silicone rubber wiper blade.
It would be desireable therefore to provide a curable silicone composition which can be readily molded to a windshield wiper blade having a superior service life and a low coefficient of friction. It also would be advantageous to provide a moldable silicone composition which can be readily converted to a brightly colored windshield wiper blade.